Back in the early US when we were still just colonies farms and crop was our early nation got almsot all of its money. We would trade with other countries and they would buy our crops, so it was natur that when we became an independent nation that we would continue to see crops. We depended on our crop market so much that it became most of our nations market. These plantations and farms built our economy almost single handedly! You would be amazed at how much plantations still help our economy.
Hope i helped! :)